The invention shortens the time required for a light projector circuit to reach a serviceable state after a power supply is switched on. The light projector circuit has a temperature measuring unit (3) which measures internal temperature; a first judgment unit (41) which judges whether set time has passed; a second judgment unit (42) which judges whether change of the internal temperature is within a specified temperature range; a control unit (43) which enables the first judgment unit (41) to act under the circumstance that change of the internal temperature is judged to be larger than the specified range; and a switching unit which, under the circumstance that change of the internal temperature is judged to be larger than the specified range, enables a drive circuit (2) to periodically act at a first interval or continuously act, and under the circumstance that set time has passed, enables the drive circuit (2) to periodically act at a second interval, the first interval period beinga period shorter than the second interval period.